Vestibular System - Lecture 12

Question 1

what is the vestibular system

Answer 1

internal system used to resolve conflict

maintenance of gaze stability

Question 2

what does the vestibular system do

Answer 2

senses position of your head in space

generate compensatory movements of the body to prevent falls or loss of balance

Question 3

what is the vestibular system able to detect

Answer 3

speed changes while driving, running, etc.

side to side movement

up/down movements

Question 4

sensory conflict

Answer 4

exists b/w the 2 sensory structures

the eyes and the ears

Question 5

what does motion sickness result from

Answer 5

conflict b/w the eyes and the ears

absence of movement

Question 6

overview of the flow of vestibular info

Answer 6

sensory input –> CN8 –> central processor –> motor output

Question 7

sensory input

Answer 7

vision

proprioception

somatosensory

peripheral vestibular system (labyrinth and otoliths)

Question 8

central processor

Answer 8

vestibular nuclei
–> along with info from the cerebral cortex and cerebellum

Question 9

motor output

Answer 9

VOR (vestibular ocular reflex)

VSR (vestibular spinal reflex - balance rxns)

Question 10

peripheral vestibular system anatomy

Answer 10

size of a dime

3 semicircular canals

2 otolith organs in each ear

Question 11

semicircular canals are sensitive to

Answer 11

angular velocity as the head turns and body rotation

Question 12

what are the semicircular canals responsible for

Answer 12

compensatory eye movements required to maintain a stable gaze

VOR

Question 13

VOR

Answer 13

vestibular ocular reflex

to maintain a stable gaze –> eye movement must occur in a direction equal and opposite to head rotation and with equal velocity

Question 14

semicircular canal orientation

Answer 14

all canals are at 90 degree angles to each other

work in pairs

Question 15

how do the canals work in pairs

Answer 15

anterior canal in one ear works with the posterior canal of the other ear

horizontal canals work together

Question 16

what do the semicircular canals have connections to

Answer 16

extra ocular muscles

planes of the canals closely match the planes of extra ocular muscles

Question 17

parts of the semicircular canals

Answer 17

ampulla

cupula

hair cells

Question 18

ampulla

Answer 18

enlargement at the end of each semicircular canal

Question 19

ampulla fxn

Answer 19

sensory organ of the canals

Question 20

ampularis

Answer 20

small crest in each ampulla

Question 21

cupula

Answer 21

gelatinous mass over the crista ampularis into which hair cells project

Question 22

what occurs as the cupula bends

Answer 22

firing of the hair cells increases or decreases depending on the direction of deflection

Question 23

hair cells

Answer 23

cells location on the crista ampularis

Question 24

where do hair cells project

Answer 24

in the cupula

connect to the vestibular N (CN8)

Question 25

endolymph

Answer 25

fluid that fills the cavities of the inner ear high in K+ and low in Na+

Question 26

perilymph

Answer 26

fluid that surround the endolymph separated from the endolymph high Na and low K+ similar to CSF

Question 27

endolymphatic sac

Answer 27

keeps fluid at constant level

Question 28

do endolymph and perilymph ever mix

Answer 28

not under normal circumstances

Question 29

hair cells --> firing rate

Answer 29

there is a resting firing rate of the vestibular N

Question 30

what happens if the hair cells are bent towards the side of movement

Answer 30

there is excitation increase in the firing rate

Question 31

what happens if the hair cells are bent in the opposite direction

Answer 31

inhibition decrease in the firing rate

Question 32

what is firing rate dependent on

Answer 32

intensity and direction of head movement

Question 33

what maintains gaze on a target when the head is moved

Answer 33

VOR - vestibular ocular reflex

Question 34

what do signals from the semicircular canals cause

Answer 34

the eyes to move in a direction equal and opposite to the head and with the same velocity

Question 35

what is the VOR mediated by

Answer 35

a reflex pathway b/w the semicircular canals and the extra ocular muscles

Question 36

abnormal VOR

Answer 36

inability to focus on objects when the head moves

Question 37

nystagmus

Answer 37

involuntary movement of the eye normally occurs when the head is moving or following a target

Question 38

what does a nystagmus consist of

Answer 38

slow component --> when the eyes slip off a target a fast phase --> the quick correction back

Question 39

what is the nystagmus named after

Answer 39

the quick phase if there is weakness on one side --> the slow component is the side of the problem

Question 40

how is a nystagmus documented

Answer 40

(+) LBN (+) RBN

Question 41

otolith

Answer 41

utricle saccule

Question 42

fxn of otolith

Answer 42

detects linear acceleration gravity VSR - vestibular spinal reflex

Question 43

VSR

Answer 43

responsible for postural adjustments needed to regain balance

Question 44

otolith structure

Answer 44

macula otoconia

Question 45

macula

Answer 45

hair cells covered by gel

Question 46

otoconia

Answer 46

calcium carbonate crystals located on the top of the gel layer that covers the macula

Question 47

what make the otolith responsible to gravity

Answer 47

weight of the crystals

Question 48

what occurs as the head moves --> otolith

Answer 48

otoconia fall to one side and cause the hair cells to fire